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Quick Freezing of Daphnia

>>Wonder if you can freeze them in ice cube form for use later?

>You can freeze them in ice cube trays, but they tend to lose their >food 
>content rather quickly once thawed, so feed them fast.
>And since they don't move around, a lot of fish tend to ignore them
>(especially bigger fish/reptiles/amphibians that would normally eat >them 
>if they moved).

I would strongly suggest you use flatpacks and not icecubes as the volume of 
icecubes is too large. It will take too long time before the animals get 
frozen; as a result you will have the formation of a small amount of 
ice-nuclei, which become bigger and bigger. These will form big icecrystals 
which will then puncture the cell walls and as a result the cell fluids will 
leach from the cells. This will lower the nutritional value of the animals 
dramatically on one side and will increase the organic load of the water on 
the other side.

Try to make as thin a layer as possible in order to achieve quick freezing 
(so more ice-nuclei will form, resulting in smaller ice-crystals, resulting 
in less damage to the product). Use plastic bags in order to prevent freezer 
burn and try to lower the temperature of the freezer compartment. With some 
practice you should end up with correctly frozen Daphnia, i.e. still 
retaining its nutrients. But of course, live Daphnia are better as their 
movement stimulates/triggers the hunting behaviour of many fish.

Steve Geerts
Biologist San Francisco Bay Brand

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